Arduino Library Import & Errors

After hours of searching on Internet without success I finally find out how to import library in Arduino IDE to work properly. I will write it down so you don't need to lose couple of hours on search without results.

Firstly, internet is full of advice and ways how to import library in Arduino but for me none of these doesn't work.

After I tried import library in the way to copy downloaded library into Arduino libraries as internet says. I got errors like this:
multiple definition of `LiquidCrystal_I2C::pulseEnable(unsigned char)'
LiquidCrystal_I2C.cpp.o: In function `LiquidCrystal_I2C::send(unsigned char, unsigned char)':

What I figured out is that the way I "import" library is totally wrong.
The way I solved it is below!

1. Download library (.zip file)
2. Open Arduino IDE 
3. Go to Sketch --> Import Library --> Add library...
4. Select your .zip file of Library --> Open
5. Now your library is Imported correctly --> Everything works, no errors!

NOTE:
Do not UNZIP Downloaded Library.



If you work with Arduino NANO and Arduino UNO the most common Error is below:
avrdude stk500_getsync() not in sync resp=0x00

To fix this ERROR Only thing you have to do is:

1. Open Arduino IDE
2. Go to Tools --> Board
3. Select appropriate Arduino 
4. That's it! Enjoy!